Semiconductor device and a method of manufacturing the same

ABSTRACT

To provide a technique capable of positioning of a semiconductor chip and a mounting substrate with high precision by improving visibility of an alignment mark. In a semiconductor chip constituting an LCD driver, a mark is formed in an alignment mark formation region over a semiconductor substrate. The mark is formed in the same layer as that of an uppermost layer wiring (third layer wiring) in an integrated circuit formation region. Then, in the lower layer of the mark and a background region surrounding the mark, patterns are formed. At this time, the pattern P 1   a  is formed in the same layer as that of a second layer wiring and the pattern P 1   b  is formed in the same layer as that of a first layer wiring. Further, the pattern P 2  is formed in the same layer as that of a gate electrode, and the pattern P 3  is formed in the same layer as that of an element isolation region.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese patent applicationNo. 2008-32666 filed on Feb. 14, 2008, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device and a method ofmanufacturing the same and more particularly to a technique which isuseful for the application to an LCD (Liquid Crystal Display) driverthat drives a liquid crystal display unit and manufacturing thereof.

In Japanese patent laid-open No. 11-330247 (patent document 1), atechnique is described, which can accurately detect an alignment markwhen forming an alignment mark for laser trimming within a chip.Specifically, the surface of a semiconductor substrate made of SOIsubstrate has a tapered part oblique with respect to the normaldirection at least in the peripheral region of the alignment mark andlaser light is caused to reflect in a direction different from thenormal direction at the tapered part. With the arrangement, it ispossible to reduce the reflection of laser light in the normal directionof the semiconductor substrate in the peripheral region of the alignmentmark, and therefore, the alignment mark can be accurately distinguishedfrom its peripheral region. Consequently, it is concluded that thedetection of an alignment mark can be accurately carried out also whenforming an alignment mark within a chip. In this case, the tapered partis formed in the same layer as that of an element isolation regionformed over the semiconductor substrate.

In Japanese patent laid-open No. 2000-182914 (patent document 2), atechnique is described, which provides a mark with which an image can bestably recognized and detected with high precision in an alignment markfor image recognition to be attached to a semiconductor device.Specifically, in the peripheral region of a cross-shaped mark main bodypart formed as a solid pattern of aluminum layer, a diffusion reflectionlayer made of aluminum is formed. As a diffusion reflection layer, astripe-shaped, grating-shaped, or dot-shaped fine pattern formed by analuminum layer can be used. Patent document 2 also describes thatopenings are formed with a fine pattern of stripe shape etc. in aninterlayer insulating film in the lower layer and an aluminum layerhaving an irregular (level differences) pattern corresponding to thepattern of the openings can be used as a diffusion reflection layer. Inthis case, the diffusion reflection layer formed in the peripheralregion of the cross-shaped mark main body part is formed in the samelayer as that of the mark main body part.

SUMMARY OF THE INVENTION

Recently, an LCD using a liquid crystal as a display element hasprevailed rapidly. The LCD is controlled by a driver that drives an LCD.An LCD driver is configured by a semiconductor chip and mounted on, forexample, a glass substrate. A semiconductor chip constituting an LCDdriver has a structure in which a plurality of transistors andmultilayer wirings is formed over a semiconductor substrate and over itssurface, bump electrodes are formed. Then, the bump electrodes formed onthe surface and the glass substrate are coupled via an anisotropicconductive film. At this time, positioning is carried out in order tocouple with high precision the bump electrodes formed over thesemiconductor chip and the wirings formed over the glass substrate. Forthe positioning, a mark called alignment is formed on the semiconductorchip and it is possible to detect the position of the semiconductor chipwith high precision by recognizing the alignment mark. For example, thecross-shaped mark is formed by a metal film in the same layer as that ofthe uppermost wiring and the alignment mark has a structure in which thecross-shaped mark is formed in the square background region having aside of about 150 p.m. The detection of the position of thesemiconductor chip is carried out by recognizing the position of thealignment mark with a camera, in which the cross-shaped mark isrecognized by utilizing the difference in contrast between thebackground region and the cross-shaped mark.

However, the difference in contrast between the cross-shaped mark andthe background region is sensitively affected by the material of themetal film constituting the mark and the film thickness of theinterlayer insulating film. Consequently, the difference in contrastbetween the mark and the background region is not even between differentsemiconductor wafers or between chip regions of the same semiconductorwafer due to the variations in the manufacturing process of thesemiconductor device and there arises a problem that the precision ofdetecting a mark is degraded.

An object of the present invention is to provide a technique capable ofpositioning of a semiconductor chip and a mounting substrate byimproving the visibility of an alignment mark.

The above and further objects and novel features of the invention willmore fully appear from the following detailed description in thisspecification and the accompanying drawings.

Among the preferred embodiments of the invention which will be disclosedherein, the typical ones will be briefly outlined below.

A semiconductor device according to a typical embodiment comprises asemiconductor chip and the semiconductor chip includes an alignment markformation region in which an alignment mark used for positioning whenmounting the semiconductor chip on a mounting substrate and anintegrated circuit formation region in which an integrated circuit isformed. In this case, the alignment mark formed in the alignment markformation region has (a) a mark region in which a mark is formed and (b)a background region that surrounds the mark region. On the other hand,in the integrated circuit formation region, (c) a plurality of elementisolation regions formed over a semiconductor substrate, (d) a MISFETformed in an active region partitioned by the element isolation regions,and (e) wirings formed over the semiconductor substrate as well as overthe MISFET are formed. The wirings are formed across a plurality oflayers and the uppermost layer wiring among the wirings and thealignment mark are formed in the same layer. Here, the embodiment ischaracterized in that a first pattern is formed in the lower layer ofthe background region of the alignment mark and the first pattern isformed in the same layer as that of the wiring in one layer formed inthe lower layer than the uppermost layer wiring in the integratedcircuit formation region.

A method of manufacturing a semiconductor device according to a typicalembodiment relates to a method of manufacturing a semiconductor devicehaving (a) an alignment mark formation region in which an alignment markused for positioning when mounting a semiconductor chip on amountingsubstrate is formed and an integrated circuit formation region in whichan integrated circuit is formed, the alignment mark including a markregion in which a mark is formed and a background region that surroundsthe mark region. The method of manufacturing a semiconductor deviceincludes the steps of (b) forming a plurality of element isolationregions in the integrated circuit formation region of a semiconductorsubstrate and (c) forming a MISFET in an active region partitioned bythe element isolation regions. The method further includes the steps of(d) forming wirings in the integrated circuit formation region as wellas over the MISFET and (e) forming an uppermost layer wiring in theintegrated circuit formation region and forming the alignment mark inthe same layer as that of the uppermost layer wiring in the alignmentmark formation region. Here, the step (d) is characterized by forming afirst pattern formed in the same layer as that of the wiring also in thelower layer of the background region in the alignment mark formationregion.

The effect brought about by a typical embodiment of the inventionsdisclosed in the present application will be briefly described asfollows.

According to a typical embodiment, it is possible to carry outpositioning of a semiconductor chip and a mounting substrate byimproving visibility of an alignment mark.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a configuration of a semiconductor chip ina first embodiment of the present invention.

FIG. 2 is a plan view showing an example of an alignment mark.

FIG. 3 is a plan view showing an example of the alignment mark.

FIG. 4 is a plan view showing an example of the alignment mark.

FIG. 5 is an enlarged diagram of part of the semiconductor chip.

FIG. 6 is a diagram showing a configuration of the alignment mark.

FIG. 7 is a section view cut along an A-A line in FIG. 5 and FIG. 6.

FIG. 8 is a section view cut along a B-B line in FIG. 5 and FIG. 6.

FIG. 9 is a diagram in which FIG. 7 and FIG. 8 are overlapped.

FIG. 10 is a diagram for illustrating a mechanism to improve visibilityof the alignment mark.

FIG. 11 is a section view showing a manufacturing process of asemiconductor device in the first embodiment.

FIG. 12 is a section view showing a manufacturing process of thesemiconductor device following FIG. 11.

FIG. 13 is a section view showing a manufacturing process of thesemiconductor device following FIG. 12.

FIG. 14 is a section view showing a manufacturing process of thesemiconductor device following FIG. 13.

FIG. 15 is a section view showing a manufacturing process of thesemiconductor device following FIG. 14.

FIG. 16 is a section view showing a manufacturing process of thesemiconductor device following FIG. 15.

FIG. 17 is a section view showing a manufacturing process of thesemiconductor device following FIG. 16.

FIG. 18 is a section view showing a manufacturing process of thesemiconductor device following FIG. 17.

FIG. 19 is a section view showing a manufacturing process of thesemiconductor device following FIG. 18.

FIG. 20 is a section view showing a manufacturing process of thesemiconductor device following FIG. 19.

FIG. 21 is a section view showing a manufacturing process of thesemiconductor device following FIG. 20.

FIG. 22 is a section view showing a manufacturing process of thesemiconductor device following FIG. 21.

FIG. 23 is a section view showing a manufacturing process of thesemiconductor device following FIG. 22.

FIG. 24 is a section view showing a manufacturing process of thesemiconductor device following FIG. 23.

FIG. 25 is a section view showing a manufacturing process of thesemiconductor device in the first embodiment.

FIG. 26 is a section view showing a manufacturing process of thesemiconductor device following FIG. 25.

FIG. 27 is a section view showing a manufacturing process of thesemiconductor device following FIG. 26.

FIG. 28 is a section view showing a manufacturing process of thesemiconductor device following FIG. 27.

FIG. 29 is a diagram showing the entire configuration of an LCD (LiquidCrystal Display).

FIG. 30 is a diagram showing a configuration of the alignment mark.

FIG. 31 is a section view cut along an A-A line in FIG. 30.

FIG. 32 is a section view cut along a B-B line in FIG. 30.

FIG. 33 is a diagram in which FIG. 31 and FIG. 32 are overlapped.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following embodiments, when necessary for the sake ofconvenience, description will be given by dividing an embodiment into aplurality of sections or embodiments, however, except when explicitlystated in particular, the sections or embodiments are not those havingnothing to do with each other but one has a relationship with another orall the rest as a variation, detail, supplementary description, etc.

When the number of elements etc. (including the number of items,numerical value, quantity, range, etc.) is referred to in the followingembodiments, except when explicitly stated in particular or when thenumber is apparently limited to a specific number in principle, thenumber is not limited to the specific number but may be greater or lessthan that.

Further, it is needless to say that, in the following embodiments,except when explicitly stated in particular or when apparentlyindispensable in principle, the components (including elementary steps)are not necessarily indispensable.

Similarly, it is assumed that, in the following embodiments, when theshapes, positional relationships, etc., of the components etc. arereferred to, except when explicitly stated or when they can apparentlybe thought otherwise in principle, those substantially similar to orresembling the shapes etc. are also included. This also applies to theabove-mentioned numerical values and ranges.

In all of the drawings for explaining the embodiments, the same partsare assigned the same symbols as a rule and its duplicated descriptionwill be omitted. In order to make the drawing easier-to-see, even a planview may be hatched.

First Embodiment

FIG. 1 is a plan view showing a configuration of a semiconductor chipCHP (semiconductor device) in a first embodiment. The semiconductor chipCHP in the first embodiment is an LCD driver. In FIG. 1, thesemiconductor chip CHP has a semiconductor substrate 1S formed into, forexample, an elongated oblong shape (rectangular shape) and over its mainsurface, an LCD driver to drive, for example, a liquid crystal displaydevice is formed. The LCD driver has a function to control theorientation of the liquid crystal molecule by supplying a voltage toeach pixel of the cell array constituting the LCD and comprises a gatedrive circuit, a source drive circuit, a liquid crystal drive circuit, agraphic RAM (Random Access Memory), a peripheral circuit, etc. Thesefunctions are realized by semiconductor devices and wirings formed onthe semiconductor substrate 1S. First, a surface configuration of thesemiconductor chip CHP will be described.

The semiconductor chip CHP has a rectangular shape with a pair of shortsides and a pair of long sides and along one of the pair of long sides(the lower side in FIG. 1), bump electrodes BP1 are arranged. These bumpelectrodes BP1 are arranged on a straight line. The bump electrode BP1functions as an external connection terminal that couples to anintegrated circuit (LCD driver) comprising semiconductor devices andwirings formed inside the semiconductor chip CHP. In particular, thebump electrode BP1 is the one for a digital input signal or an analoginput signal.

Next, along the other long side of the pair of long sides (the upperside in FIG. 1), bump electrodes BP2 are arranged. These bump electrodesBP2 are also arranged on a straight line along the long side, however,the arrangement density of the bump electrodes BP2 is higher than thatof the bump electrodes BP1. That is, the bump electrodes BP1 and thebump electrodes BP2 are formed along the long sides opposing each otherof the semiconductor substrate 1S and the number of bump electrodes BP2is larger than that of bump electrodes BP1. These bump electrodes BP2also function as an external connection terminal that couples theintegrated circuit formed inside the semiconductor substrate 1S and theoutside. In particular, the bump electrode BP2 is the one for an outputsignal from the LCD driver.

As described above, along the pair of long sides constituting theperiphery of the semiconductor chip CHP, the bump electrodes BP1 and thebump electrodes BP2 are formed. In this case, because the number of bumpelectrodes BP2 is larger compared to that of bump electrodes BP1, thearrangement density of the bump electrodes BP2 is higher than that ofthe bump electrodes BP1. This is because while the bump electrode BP1 isthe one for an input signal input to the LCD driver, the bump electrodeBP2 is the one for an output signal output from the LCD driver. That is,the input signal input to the LCD driver is serial data, and therefore,the number of bump electrodes BP1, which are an external connectionterminal, becomes not so large. In contrast to this, the output signaloutput from the LCD driver is parallel data, and therefore, the numberof bump electrodes BP2, which are an external connection terminal,becomes large. That is, the bump electrode BP2 for an output signal isprovided for each cell (pixel) constituting a liquid crystal element,and therefore, the number of bump electrodes BP2 corresponding to thenumber of cells is necessary. As a result, the number of bump electrodesBP2 for an output signal is larger compared to the number of bumpelectrodes BP1 for an input signal. Consequently, the number of bumpelectrodes BP2 is increased larger than the number of bump electrodesBP1.

In FIG. 1, the bump electrodes BP1 and the bump electrodes BP2 arearranged along the pair of long sides constituting the semiconductorchip CHP, however, it may also be possible to arrange bump electrodesalong the pair of short sides besides the pair of long sides. In thefirst embodiment, the bump electrodes BP2 for an output signal arearranged in one row, however, it is also possible to arrange them in tworows in a staggered manner. As described above, the number of bumpelectrodes BP2 for an output signal may become tremendously largercompared to the number of bump electrodes BP1 for an input signal, andtherefore, there may be the case where they cannot be arranged in onerow even if they are arranged densely on one straight line. In such acase, it is possible to arrange the many bump electrodes BP2 for anoutput signal by arranging them in two rows.

Subsequently, as shown in FIG. 1, on the semiconductor chip CHP, analignment mark AM for positioning is formed. For example, the alignmentmark AM is formed in the number of two on both ends of the long sidealong which the bump electrodes BP1 for an input signal are arranged onone straight line. The alignment mark is used for positioning.Specifically, the alignment mark AM is used not for positioning in thephotolithography technique but for positioning when mounting thesemiconductor chip CHP over a glass substrate. That is, thesemiconductor chip CHP, which is an LCD driver, is mounted over theglass substrate constituting a liquid crystal display device. In thiscase, the semiconductor chip CHP is mounted in the glass substrate bycoupling the bump electrodes BP1, BP2 formed in the semiconductor chipCHP to electrodes (ITO electrodes, transparent electrodes) formed overthe glass substrate via an anisotropic conductive film. The distancesbetween the bump electrodes BP1 and the bump electrodes BP2 are verysmall and the electrodes provided in correspondence with the bumpelectrodes BP1 and the bump electrodes BP2 are also arranged verydensely. As a result, if the mounting position of the semiconductor chipCHP shifts, if slightly, it is no longer possible to correctly couplethe bump electrodes BP1 and BP2 to the electrodes over the glasssubstrate and there is a possibility that the bump electrodes BP1 andBP2 come into contact also with the neighboring electrodes, causing ashort circuit failure. Consequently, it can be seen that the bumpelectrodes BP1 and BP2 formed over the semiconductor chip CHP and theelectrodes formed over the glass substrate need to be positionedaccurately. Therefore, in order to recognize the position of thesemiconductor chip CHP accurately, the alignment mark AM is provided. Byrecognizing the alignment mark AM with a camera, it is possible toobtain the coordinates of the accurate position of the semiconductorchip CHP. As a result, it is possible to arrange the semiconductor chipCHP with high precision over the glass substrate by coupling the bumpelectrodes BP1, BP2 of the semiconductor chip CHP and the electrodes ofthe glass substrate while recognizing the alignment mark AM with acamera.

In the following, a configuration of the alignment mark AM formed overthe semiconductor chip CHP will be described. FIG. 2 is a plan viewshowing a configuration example of the alignment mark AM in the firstembodiment. As shown in FIG. 2, the alignment mark AM has a shape inwhich a cross-shaped mark MK1 is formed in the center of a squarebackground region BG. The background region BG is a square region with aside length of, for example, about 150 μm and made of, for example, aninsulating film such as a silicon oxide film. On the other hand, thecross-shaped mark MK1, which is formed inside the background region BG,is made of, for example, a metal film. By making up the backgroundregion BG and the mark MK1 by different materials in this manner, whenthe alignment mark AM is irradiated with light, the reflectivity of thelight reflected from the background region BG is different from that ofthe light reflected from the mark MK1. Since the reflectivity of thelight reflected from the background region BG is different from that ofthe mark MK1, there is generated a difference in contrast between thebackground region BG and the mark MK1 and therefore the mark MK1 can berecognized with a camera. In general, the reflectivity of a metal filmsuch as an aluminum film is higher than that of an insulating film suchas a silicon oxide film, and therefore, the bright mark MK1 emerges overthe dark background region BG and thus the mark MK1 can be recognized.

FIG. 2 shows the shape of a cross as an example of the mark MK1constituting the alignment mark AM, however, this is not limited andthere can be thought various mark shapes. For example, FIG. 3 is a planview showing another configuration example of the alignment mark AM. Asshown in FIG. 3, a mark MK2 is formed within the background region BGand the shape of the mark MK2 is composed of a cross and a squareprovided in the upper left of the cross. Further, FIG. 4 is a plan viewshowing another configuration example of the alignment mark AM. In thealignment mark AM shown in FIG. 4, a circular mark MK3 is formed in thebackground region BG. As described above, various shapes of a mark canbe thought, such as a cross, a modification of a cross, and a circularshape, as shown in FIG. 2 to FIG. 4, and it is possible to use any shapefor the positioning of the semiconductor chip CHP.

As described above, the alignment mark AM is recognized by thedifference in contrast between the background region BG and the markMK1, however, the present inventors have found that with theconventional alignment mark AM, the recognition of the alignment mark AMis impeded resulting from the unevenness of the difference in contrastbetween the background region BG and the mark MK1. That is, in theconventional alignment mark AM, there is a remarkable amount of lightreflected from the background region, and therefore, the difference incontrast between the background region BG and the mark MK1 becomessmaller, making it difficult to sufficiently recognize the mark MK1 witha camera. Specifically, it has been revealed that the light reflectedfrom the background region BG sensitively depends on the film thicknessof an insulating film constituting the background region BG. Owing tothe variations in the manufacture process, there is a possibility thatvariations in the film thickness of the insulating film constituting thebackground region BG of the alignment mark AM are caused in differentsemiconductors wafer or in different chip regions of the samesemiconductor wafer. In this case, in the semiconductor chip CHPobtained from a different semiconductor wafer or from a different chipregion of the same semiconductor wafer, the difference in contrastbetween the background region BG and the mark MK1 is not even andvariations are caused resulting from the difference in the filmthickness of the insulating film constituting the background region BG.The situation has been brought about in which, for example, in one ofthe semiconductor chips CHP, the difference in contrast between thebackground region BG and the mark MK1 of the alignment mark AM becomeslarge and the alignment mark can be recognized with a camera, however,on the other hand, in another of the semiconductor chips CHP, thedifference in contrast between the background region BG and the mark MK1of the alignment mark AM becomes small and it is difficult to recognizethe alignment mark AM with a camera. That is, with the conventionalalignment mark AM, the difference in contrast between the backgroundregion BG and the mark MK1 differs from semiconductor chip CHP tosemiconductor chip CHP, resulting in the reduction of the visibility ofthe alignment mark AM. Therefore, an object of the first embodiment isto provide a technique capable of improving the visibility of thealignment mark AM in all of the semiconductor chips CHP even if thedifference in contrast between the background region BG and the mark MK1varies resulting from, for example, the difference in the film thicknessof the insulating film constituting the background region BG of thealignment mark AM. In order to achieve this object, in the firstembodiment, it is basically intended that the visibility of thealignment mark AM can be improved even if the difference in contrastbetween the background region BG and the mark MK1 of the alignment markAM varies. Specifically, in the first embodiment, a dot pattern isformed in the lower layer of the background region BG of the alignmentmark AM. Consequently, it is possible to reduce the proportion of lightreflected from the background region BG by causing the functions todiffract, scatter, and shut off the light that has entered thebackground region BG to exhibit their abilities. Due to the effect ofreduction in reflected light by the dot pattern provided in the lowerlayer of the background region BG, the difference in contrast betweenthe background region BG and the mark MK1 is improved. In other words,in the first embodiment, by adopting a configuration in which the lightreflected from the background region BG can be reduced sufficiently, itis possible to maintain a difference in contrast sufficient for a camerato recognize the difference in all of the semiconductor chips CHP evenif the difference in contrast between the background region BG and themark MK1 varies resulting from, for example, the difference in the filmthickness of the insulating film constituting the background region BG.That is, even if the difference in contrast between the backgroundregion BG and the mark MK1 varies in the individual semiconductor chips,in the first embodiment, the light reflected from the background regionBG can be reduced absolutely, and therefore, it is possible to obtain adifference in contrast sufficiently satisfactory for the recognitionwith a camera. The first embodiment is based on the technical conceptfrom the standpoint that the visibility of the alignment mark AM isimproved without the influence of the variations in the difference incontrast by reducing the light reflected from the background region BGabsolutely even if the difference in contrast varies in the individualsemiconductor chips CHP, rather than that the variations in thedifference in contrast in the individual semiconductor chips CHP aresuppressed positively.

The configuration of the alignment mark AM in the first embodiment willbe described below in detail. FIG. 5 is an enlarged plan view of thevicinity of the alignment mark formation region of the semiconductorchip CHP in FIG. 1. In FIG. 5, a guard ring GR is formed so as tosurround the outer edge part of the semiconductor chip CHP and in acorner within the guard ring GR, the alignment mark AM is formed. Then,beside the alignment mark AM, the bump electrodes BP1 for an inputsignal are arranged. Here, for the description of the characteristicconfiguration of the alignment mark AM in the first embodiment, sectionviews are used, that is, for the description, a section view of theconfiguration cut by an A-A line in FIG. 5 and a section view cut by aB-B line in FIG. 5 are used. First, in order to explain the differencebetween the A-A line and the B-B line in FIG. 5, FIG. 6 shows whichregion of the alignment mark AM is cut by the respective lines using anenlarged plan view of the alignment mark AM in the first embodiment.

FIG. 6 is a plan view showing the configuration of the alignment mark AMin the first embodiment. As shown in FIG. 6, in the alignment mark AM inthe first embodiment, the cross-shaped mark MK1 is formed in the centerof the rectangular background region BG. Then, in the lower layer of thebackground region BG including the lower layer of the mark MK1, a dotpattern is formed. The dot pattern shown in FIG. 6 is not in the samelayer as that of the mark MK1 but is formed across the lower layer ofthe mark MK1 and the lower layer of the background region BG. The dotpattern shown in FIG. 6 is not formed in the same layer but shown as apattern formed by overlapping in a planar manner those formed across twoor more layers. For example, the dot pattern crossed by the A-A line inFIG. 6 shows a pattern P1 a, and further showing a pattern P3 also,which is a planar pattern similar to the pattern P1 a although formed ina different layer from that of the pattern P1 a. That is, the A-A linein FIG. 6 is a line that cuts the arrangement region of the pattern P1 aand the pattern P3 constituting the dot pattern. On the other hand, thedot pattern crossed by the B-B line in FIG. 6 shows a pattern P1 b, andfurther showing a pattern P2 also, which is a planar pattern similar tothe pattern P1 b although formed in a different layer from that of thepattern P1 b. That is, the B-B line in FIG. 6 is a line that cuts thearrangement region of the pattern P1 b and the pattern P2 constitutingthe dot pattern. In this manner, the dot pattern formed in the alignmentmark AM in FIG. 6 is configured by alternately arranging the patterns(P1 a and P3) on the A-A line and the patterns (P1 b and P2) on the B-Bline.

Based on such a configuration, a section view cut by the A-A line inFIG. 5 and FIG. 6 is shown in FIG. 7. As shown in FIG. 7, in the sectioncut by the A-A line, a guard ring region, an alignment mark region, andan integrated circuit formation region are shown schematically. In thefollowing, a structure formed in each region will be described.

First, a guard ring structure formed in the guard ring region will bedescribed. The guard ring structure is formed to prevent the invasion ofwater and impurities into the semiconductor chip CHP. Over the mainsurface (element formation surface) of the semiconductor substrate 1S,an element isolation region STI is formed and an active region ispartitioned between the two element isolation regions STI. Over the mainsurface of the semiconductor substrate 1S over which the elementisolation region STI is formed, a laminated film of a silicon nitridefilm 7 and a silicon oxide film 8 is formed and a plug PLG1 is formed soas to penetrate through the laminated film. In the plug PLG1, forexample, a titanium/titanium nitride film, which is a barrier conductivefilm, is formed over the surface of its hole and over thetitanium/titanium nitride film, a tungsten film is formed. That is, theplug PLG1 is formed by filling its hole with a titanium/titanium nitridefilm and a tungsten film. Then, over an interlayer insulating film madeup of the silicon nitride film 7 and the silicon oxide film 8, a wiringGR1 is formed and the wiring GR1 is electrically coupled with the plugPLG1. Next, over the silicon oxide film 8 as well as over the wiringGR1, a silicon oxide film 9 is formed and in the silicon oxide film 9, aplug PLG2 that penetrates through the silicon oxide film 9 and iscoupled with the wiring GR1 is formed. Similar to the plug PLG1, theplug PLG2 is also formed by filling its hole with a titanium/titaniumnitride film and a tungsten film. Further, over the silicon oxide film 9in which the plug PLG2 is formed, a wiring GR2 is formed and a siliconoxide film 10 is formed so as to cover the wiring GR2. The wiring GR2 iselectrically coupled with the plug PLG2 that penetrates through thesilicon oxide film 9. Then, in the silicon oxide film 10, a plug PLG3that penetrates through the silicon oxide film 10 is formed and over thesilicon oxide film 10 in which the plug PLG3 is formed, a wiring GR3 isformed. The plug PLG3 also has the same structure as that of the plugPLG1 and plug PLG2 and is formed by filling its hole with atitanium/titanium nitride film and a tungsten film. Over the siliconoxide film 10 as well as over the wiring GR3, a silicon oxide film 11and a silicon nitride film 12 are formed. The wirings GR1, GR2 and GR3are formed by, for example, an aluminum alloy film. As described above,the guard ring structure is formed in the guard ring region. That is, byforming a protective wall structure by the plugs PLG1 to PLG3 and thewirings GR1 to GR3, the invasion of water and impurities into thealignment mark formation region and the integrated circuit formationregion formed on the inside than the guard ring region is prevented.

Subsequently, a transistor and a wiring formed in the integrated circuitformation region will be described. In FIG. 7, an n-channel type MISFET(Metal Insulator Semiconductor Field Effect Transistor) constitutingpart of the integrated circuit is shown. Here, the n-channel type MISFETand a wiring will be described. Although not shown schematically in FIG.7, a p-channel type MISFET etc. is also formed in addition to then-channel type MISFET in the integrated circuit formation region.

Over the main surface of the semiconductor substrate 1S, a plurality ofthe element isolation regions STI is formed and a region partitioned bythe element isolation region STI is an active region. The elementisolation region STI is formed by, for example, embedding a siliconoxide film in a groove formed in the semiconductor substrate 1S.

In the active region partitioned by the element isolation region STI, ap-type well PWL is formed. The p-type well PWL is formed by introducingp-type impurities such as boron (B), into the semiconductor substrate1S. The n-channel type MISFET is formed over the p-type well PWL. Theconfiguration of the n-channel type MISFET will be described.

In the n-channel type MISFET, for example, a gate insulating film 2 madeof a very thin silicon oxide film is formed over the p-type well PWL anda gate electrode G is formed over the gate insulating film 2. The gateelectrode G is formed by, for example, a polysilicon film. The gateelectrode G may have a laminated structure of a polysilicon film and asilicide film by forming a silicide film such as a cobalt silicide film,over the surface of the polysilicon film constituting the gate electrodeG. In this case, the resistance of the gate electrode G can be reducedby the silicide film.

On the sidewalls on both sides of the gate electrode G, a sidewall 5made of, for example, a silicon oxide film is formed and in the p-typewell PWL immediately under the sidewall 5, a low-concentration n-typeimpurity diffusion region 4 is formed. The low-concentration n-typeimpurity diffusion region 4 is also called an extension region andformed aligned with the gate electrode G. The low-concentration n-typeimpurity diffusion region 4 is a semiconductor region formed byintroducing n-type impurities such as phosphorus (P) and arsenic (As)into the semiconductor substrate 1S. Subsequently, on the outside of thelow-concentration n-type impurity diffusion region in the p-type wellPWL, a high-concentration n-type impurity diffusion region 6 is formed.The high-concentration n-type impurity diffusion region 6 is also asemiconductor region into which n-type impurities such as phosphorus andarsenic are introduced and the concentration of the introduced n-typeimpurities is higher than that of the low-concentration n-type impuritydiffusion region 4. The high-concentration n-type impurity diffusionregion 6 is formed aligned with the sidewall 5. The source region andthe drain region are formed by these low-concentration n-type impuritydiffusion region 4 and high-concentration n-type impurity diffusionregion 6. That is, by forming each of the source region and the drainregion by combining the low-concentration n-type impurity diffusionregion 4 and the high-concentration n-type impurity diffusion region 6,an LDD (Lightly Doped Drain) structure capable of relaxing theconcentration of electric field immediately under the end part of thegate electrode can be obtained. In this manner, the n-channel typeMISFET is formed.

Subsequently, the wiring structure formed in the upper layer of then-channel type MISFET will be described. As shown in FIG. 7, aninterlayer insulating film made up of the silicon nitride film 7 and thesilicon oxide film 8 is formed so as to cover the n-channel type MISFET.In the interlayer insulating film, the plug PLG1 that reaches the sourceregion or the drain region of the n-channel type MISFET is formed. Theplug PLG1 has the same structure as that of those formed in the guardring region and is formed by embedding a titanium/titanium nitride filmand a tungsten film in the hole. Then, over the plug PLG1, for example,a first layer wiring L1 made of an aluminum alloy film is formed and thefirst layer wiring L1 and the plug PLG1 are electrically coupled.Further, over the silicon oxide film 8 in which the first layer wiringL1 is formed, the silicon oxide film 9 is formed and the plug PLG2 thatpenetrates through the silicon oxide film 9 and reaches the first layerwiring L1 is formed. Similar to the plug PLG1, the plug PLG2 is alsoformed by embedding a titanium/titanium nitride film and a tungsten filmin the hole.

Next, over the silicon oxide film 9 in which the plug PLG2 is formed,for example, a second layer wiring L2 made of an aluminum alloy film isformed and the silicon oxide film 10 is formed so as to cover the secondlayer wiring L2. In the silicon oxide film 10, the plug PLG3 thatpenetrates through the silicon oxide film 10 and is coupled to thesecond layer wiring L2 is formed and over the plug PLG3, for example, athird layer wiring L3 made of an aluminum alloy film is formed. Similarto the plug PLG1 and the plug PLG2, the plug PLG3 is also formed byembedding a titanium/titanium nitride film and a tungsten film in thehole.

Over the silicon oxide film 10 as well as over the third layer wiringL3, a laminated film made up of the silicon oxide film 11 and thesilicon nitride film 12 is formed. In the laminated film, an opening 13that penetrates through the laminated film and exposes the surface ofthe third layer wiring L3 is formed. From the interior of the opening 13onto the silicon nitride film 12, a laminated film of a UBM (Under BumpMetal) film 14 and gold film 17 is formed and the bump electrode BP1made up of the UBM film 14 and the gold film 17 is formed. In thismanner, the n-channel type MISFET and multilayer wirings are formed inpart of the integrated circuit formation region.

Next, the alignment mark formation region, which is the characteristicregion of the first embodiment will be described. As shown in FIG. 7, inthe alignment mark formation region, over the main surface of thesemiconductor substrate 1S, the pattern P3 is formed. The pattern P3constitutes part of the dot pattern in FIG. 6. The pattern P3 has thesame structure as that of the element isolation region STI and is formedby embedding a silicon oxide film in the groove formed in thesemiconductor substrate 1S. The pattern 3 is formed in the same layer asthat of the element isolation region STI formed in the integratedcircuit formation region and one of the patterns P3 is miniaturized to asize about that of visible light. Specifically, the size of the groovethat constitutes the pattern P3 is, for example, about 400 to 800 nm.The pattern Ps is formed across the entire alignment mark formationregion. That is, the pattern P3 is formed not only in the backgroundregion in which the mark MK1 is not formed but also in the lower layerin which the mark MK1 is formed in the alignment mark formation region.

Then, in the upper layer of the pattern. P3, a laminated film made up ofthe silicon nitride film 7 and the silicon oxide film 8 is formed andover the laminated film, the silicon oxide film 9 is formed. Over thesilicon oxide film 9, the pattern P1 a is formed. The pattern P1 aconstitutes part of the dot pattern in FIG. 6. The pattern P1 a isformed in the same layer as that of the second layer wiring L2 formed inthe integrated circuit formation region and is formed by an aluminumalloy film similar to the second layer wiring L2. One of the patterns P1a is miniaturized to a size about that of visible light. Specifically,the size of the pattern P1 a is, for example, about 400 to 800 nm. Thepattern P1 a is formed across the entire alignment mark formationregion. That is, the pattern P1 a is formed not only in the backgroundregion in which the mark MK1 is not formed but also in the lower layerin which the mark MK1 is formed in the alignment mark formation region.The pattern P1 a formed in the same layer as that of the second layerwiring L2 is formed as a pattern that overlaps the pattern P3 formed inthe same layer as that of the element isolation region STI in a planarmanner.

Next, the silicon oxide film 10 is formed so as to cover the pattern P1a and over the silicon oxide film 10, the mark MK1 is formed. The markMK1 is formed in the same layer as that of the third layer wiring L3formed in the integrated circuit formation region and is formed by, forexample, an aluminum alloy film. A laminated film made up of the siliconoxide film 11 and the silicon nitride film 12 is formed so as to coverthe mark MK1. As described above, the mark MK1 is formed in thealignment mark formation region and in the lower layer of the mark MK1,the pattern P1 a and the pattern P3 are formed.

One of the characteristics of the first embodiment is that the patternP1 a and the pattern P3 are formed in the lower layer of the mark MK1.By forming the pattern P1 a and the pattern P3, the reflection of lightcan be reduced in the background region surrounding the mark MK1 in thealignment mark formation region. Consequently, almost all incident lightis reflected from the mark MK1, however, the reflected light in thebackground at the periphery of the mark MK1 can be reduced and it ispossible to increase the difference in contrast between the mark MK1 andthe background region. As a result, the visibility of the mark MK1 canbe improved and the positioning precision of the semiconductor chip canbe improved. The mechanism capable of reducing reflected light in thebackground region by providing the pattern P1 a and the pattern P3 willbe described later.

Next, FIG. 8 is a section view cut by the B-B line in FIG. 5 and FIG. 6.In FIG. 8, the configuration of the guard ring region and the integratedcircuit formation region is the same as that in section view cut by theA-A line shown in FIG. 7, and therefore, its explanation is omitted. Thealignment mark formation region, which is the characteristicconfiguration in FIG. 8, will be described as to points different fromthose in FIG. 7. The characteristic configuration in FIG. 8 is that thepattern P2 is formed over the main surface of the semiconductorsubstrate 1S. The pattern P2 is formed in the same layer as that of thegate electrode G formed in the integrated circuit formation region.Then, the pattern P2 is formed by a polysilicon film similar to the gateelectrode G. One of the patterns P2 is miniaturized to a size about thatof visible light. Specifically, the size of the pattern P2 is, forexample, about 400 to 800 nm. The pattern P2 is formed across the entirealignment mark formation region. That is, the pattern P2 is formed notonly in the background region in which the mark MK1 is not formed butalso in the lower layer in which the mark MK1 is formed in the alignmentmark formation region.

Subsequently, the characteristic configuration in FIG. 8 is one in whichthe pattern P1 b is formed over the silicon oxide film 8. The pattern P1b is formed in the same layer as that of the first layer wiring L1formed in the integrated circuit formation region and made up of analuminum alloy film that is the same material as that of the first layerwiring One of the patterns P1 b is miniaturized to a size about that ofvisible light. Specifically, the size of the pattern P1 b is, forexample, about 400 to 800 nm. The pattern P1 b is formed across theentire alignment mark formation region. That is, the pattern P1 b isformed not only in the background region in which the mark MK1 is notformed but also in the lower layer in which the mark MK1 is formed inthe alignment mark formation region. The pattern P1 b formed in the samelayer as that of the first layer wiring L1 is formed as a pattern thatoverlaps the pattern P2 formed in the same layer as that of the gateelectrode G in a planar manner.

As described above, in the first embodiment, the pattern P1 a and thepattern P3 are formed in the lower layer of the mark MK1 in thealignment mark formation region as shown in the section view (FIG. 7)cut by the A-A line and the pattern P1 b and the pattern P2 are formedin the lower layer of the mark MK1 in the alignment mark formationregion as shown in the section view (FIG. 8) cut by the B-B line. Then,in the first embodiment, the patterns P1 a, P1 b, P2, and P3 are formedin different layers from one another, respectively.

FIG. 9 is a diagram in which FIG. 7 and FIG. 8 are overlapped. From FIG.9, the positional relationship between the mark MK1 in the alignmentmark formation region and the patterns P1 a, P1 b, P2, and P3 formed inthe lower layer of the background region surrounding the mark MK1. Thatis, the pattern P1 a formed in the same layer as that of the secondlayer wiring L2 and the pattern P3 formed in the same layer as that ofthe element isolation region STI are identical from a planar standpoint,and therefore, the pattern P1 a and the pattern P3 overlap each otherwhen viewed in a planar perspective (refer to FIG. 6). Then, the patternP1 b formed in the same layer as that of the first layer wiring L1 andthe pattern 2 formed in the same layer as that of the gate electrode Gare identical from a planar standpoint and the pattern P1 b and thepattern P2 overlap each other when viewed in a planar perspective (referto FIG. 6). On the other hand, the pattern P1 a and the pattern P1 b areformed so as to be shifted from each other and the pattern P1 a and thepattern P1 b are arranged so as not to overlap each other in a planarmanner. That is, the pattern P1 a (pattern P3) shown in FIG. 7 and thepattern P1 b (pattern P2) shown in FIG. 8 are arranged so as not tooverlap each other in a planar manner. By arranging the patterns P1 a,P1 b, P2 and P3 in this manner, the dot pattern shown in FIG. 6 isformed.

Next, the mechanism capable of reducing light reflected from thebackground region by forming the patterns P1 a, P1 b, P2 and P3 in thelower layer of the mark formation region and the background region as inthe first embodiment will be described with reference to FIG. 10.

First, a first mechanism capable of reducing reflected light from thebackground region will be described. In FIG. 10, if attention is focusedon the pattern P1 a, it can be seen that each pattern P1 a is formedwith a size of visible light and the patterns P1 a are arranged atintervals of a size of visible light. The pattern P1 a arranged in thismanner has a function as a diffraction grating. A diffraction gratingspreads light incident to the diffraction grating by diffraction and thelight spread by diffraction is characterized by forming an interferencepattern (including bright fringes and dark fringes). The spread bydiffraction of the diffraction grating becomes greater as the intervalof the pattern P1 a becomes narrower. In the first embodiment, theinterval of the pattern P1 a is reduced to as small as a size of visiblelight and therefore the spread by diffraction is considerably great. Asa result, for example, light incident to the alignment mark formationregion formed in the semiconductor chip CHP enters the silicon nitridefilm 12 and the silicon oxide film 11 formed in the uppermost layer,however, the silicon nitride film 12 and the silicon oxide film 11 arealmost transparent to visible light and therefore the incident lightpasses through the silicon nitride film 12 and the silicon oxide film 11and enters the pattern P1 a. The pattern P1 a itself is made up of ametal film and therefore does not transmit the incident light butreflects it, however, the pattern P1 a is arranged regularly at theinterval of a size of visible light and therefore it functions as adiffraction grating. Since the size of the opening formed between thepatterns P1 a is the size of visible light, the effect of diffraction ismagnified. As a result, the light reflected from the pattern P1 a willspread considerably. This will reduce the amount of reflected light thatenters a camera arranged in a fixed direction. On the other hand, lightincident to the mark MK1 is reflected almost entirely because the markMK1 itself is formed by a metal film. As a result, the differencebetween the amount of reflected light diffracted by the pattern P1 a andthe amount of light reflected by the mark MK1 becomes larger. This meansthat the amount of reflected light from the background region, whichlight enters the camera, reduces due to the diffraction effect by thepattern P1 a and that the difference in contrast between the backgroundregion and the mark MK1 becomes larger. Consequently, the visibility ofthe mark MK1 with a camera is improved. As the result of the improvementof the visibility of the mark MK1 by such a first mechanism, it is madepossible to grasp with high precision the position of the semiconductorchip CHP. In particular, in the first embodiment, in addition to thepattern P1 a, the pattern P1 b, the pattern P2, and the pattern P3 areformed and each pattern functions as a diffraction grating.Consequently, the spread by diffraction of light reflected from thebackground region becomes greater and the amount of reflection lightthat enters the camera from the background region further reduces andtherefore a remarkable effect can be obtained that the difference incontrast between the mark MK1 and the background region can be madelarge sufficiently. Further, the light output from the diffractiongrating interferes with each other. By this interference, aninterference contrast pattern (including bright fringes and darkfringes) is formed. Consequently, by adjusting the position at which thecamera is arranged so that a weak pattern (including dark fringes) ofthe contrast pattern by interference enters the camera, it is possibleto further reduce the intensity of the light reflected from thebackground region. It can be seen that if the patterns P1 a, P1 b, P2and P3 are provided in the lower layer of the background region as inthe first embodiment, it is possible to reduce the amount of reflectedlight that enters the camera from the background region due to theeffect of diffraction and interference of light.

Further, there exists a second mechanism capable of reducing the amountof reflected light from the background region by the patterns P1 a, P1b, P2 and P3, in addition to the first mechanism that makes use ofdiffraction and interference of light as described above. This secondmechanism will be described. The second mechanism is realized in amanner such that, on one hand, the pattern P1 a and the pattern P1 bformed in the wiring layer cut off the reflected light and, on the otherhand, the pattern P2 and the pattern P3 formed in the lower layer of thewiring layer scatter light. Part of light incident to the pattern P1 aformed in the same layer as that of the second layer wiring L2 isreflected from the pattern P1 a and the rest passes through the openingof the pattern P1 a (interval region of the pattern P1 a) and reachesthe lower layer. Then, part of the incident light that has passedthrough the pattern P1 a is reflected from the pattern P1 b and the restpasses through the pattern P1 b. At this time, part of the lightreflected from the pattern P1 b is cut off by the pattern P1 a arrangedin the upper layer of the pattern P1 b. Consequently, the reflectedlight output from the background region can be reduced. That is, thepattern P1 a has a function to cut off part of the light that has oncepassed through the pattern P1 a and is reflected from the pattern P1 b.Further, the light that has passed through the pattern P1 b is alsoreflected from the semiconductor substrate 1S, however, part of thelight is cut off again by the pattern P1 b or the pattern P1 a. Asdescribed above, in the first embodiment, one of the characteristics isthat the pattern P1 a and the pattern P1 b are provided in the wiringlayer arranged in the middle of the mark MK1 and the semiconductorsubstrate 1S. By arranging the pattern P1 a and the pattern P1 b in thewiring layer, the effect of cutting off the light reflected in the lowerlayer of the respective patterns can be obtained. As a result that theoutput of light can be cut off by the pattern P1 a and the pattern P1 b,the amount of reflected light that enters the camera from the backgroundregion can be reduced. Further, by forming the pattern P1 a and thepattern P1 b in the plurality of layers constituting the wiring layerand by arranging the pattern P1 a and the pattern P1 b so that they donot overlap in a planar manner, the effect of cutting off by the patternP1 a and the pattern P1 b can be exhibited to the maximum. For example,part of light can be cut off by the pattern P1 b, however, part of lightpasses through the gap between the patterns P1 b. Consequently, byshifting the arrangement of the patterns P1 b in a planar manner withrespect to that of the patterns P1 a, the light that cannot be cut offby the pattern P1 b can be cut off by the pattern P1 a. From this, itcan be seen that shifting the arrangement of the patterns P1 a in aplanar manner with respect to the arrangement of the patterns P1 b iseffective from the standpoint of the cut off of the light reflected inthe lower layer of the pattern P1 a or the pattern P1 b of thesemiconductor substrate 1S etc.

Further, the provision of the pattern P2 and the pattern P3 in the lowerlayer of the pattern P1 a and the pattern P1 b is also effective fromthe standpoint of the reduction in the amount of light output from thebackground region. That is, irregularities are formed at the surface ofthe semiconductor substrate 1S by the pattern P2 and the pattern P3.Consequently, the light that has passed through the pattern P1 a and thepattern P1 b reaches the semiconductor substrate 1S. At this time, ifthe surface of the semiconductor substrate 1S is flat, the direction ofthe reflected light converges in a certain direction. If the convergeddirection is a direction in which light passes through the pattern P1 band the pattern P1 a, it is no longer possible to cause the effect ofcut off by the pattern P1 a and the pattern P1 b to exhibitsufficiently. In contrast to this, by forming the pattern P2 and thepattern P3 over the surface of the semiconductor substrate 1S, it ispossible to form irregularities over the surface of the semiconductorsubstrate 1S. If the irregularities are formed over the surface of thesemiconductor substrate 1S, light is scattered by the irregularities.That is, light incident to the semiconductor substrate 1S is scatteredand light is output in unspecified directions. In this case, the amountof light that is cut off without passing through the pattern P1 a andthe pattern P1 b increases. That is, by forming the pattern P2 and thepattern P3 in the lower layer of the pattern P1 a and the pattern P1 b,it is possible to make random the direction of the light reflected fromthe semiconductor substrate 1S. As a result, it is possible to preventthe reflected light from converging in the direction in which lightpasses through the pattern P1 a and the pattern P1 b and the effect ofcut off by the pattern P1 a and the pattern P1 b can be improved.

As described above, by arranging the pattern P1 a and the pattern P1 bin the same layer as that of the wiring layer between the semiconductorsubstrate 1S and the mark MK1, the cut off effect of the light′reflected in the lower layer of the pattern P1 a and the pattern P1 bcan be obtained. Further, by forming the pattern P2 and the pattern P3over the surface of the semiconductor substrate 1S, it is possible toimprove the cut off effect of the light by the pattern P1 a and thepattern P1 b. That is, by forming the patterns P1 a, P1 b, P2 and P3 asin the first embodiment, the sufficient cut off effect that makes use ofscattering of light can be obtained. It can be seen that the amount ofreflected light that enters the camera from the background region can bereduced by the effect of the scattering and cut off of light due to thesecond mechanism described above.

Next, a third mechanism will be described, which can make large thedifference in contrast between the MK1 and the background region byforming the patterns P1 a, P1 b, P2 and P3. Conventionally, the patternsP1 a, P1 b, P2, and P3 are not formed in the lower layer of the mark MK1in the alignment mark formation region. That is, in the alignment markformation region, the mark MK1 is formed in the same layer as that ofthe uppermost layer wiring (wiring L3) formed in the integrated circuitformation region, however, the patterns P1 a, P1 b, P2 and P3 are notformed in the lower layer of the mark MK1. In this case, the followingsituation is brought about. For example, in the integrated circuitformation region, the gate electrode G of the n-channel type MISFET isformed and over the gate electrode G, the first layer wiring L1 isformed via the interlayer insulating film (the silicon nitride film 7and the silicon oxide film 8). Then, over the first layer wiring L1, thesecond layer wiring L2 is formed via the silicon oxide film 9 and overthe second layer wiring L2, the third layer wiring L3 is formed via thesilicon oxide film 10. In contrast to this, in the conventionalalignment mark formation region, no pattern is formed in the same layeras that of the gate electrode G (pattern P2), in the same layer as thatof the first layer wiring L1 (pattern P1 b), nor in the same layer asthat of the second layer wiring L2 (pattern P1 a). Consequently, forexample, the flatness of the silicon oxide film 8 formed so as to coverthe gate electrode G is degraded. That is, in the integrated circuitformation region, the silicon oxide film 8 is formed so as to cover thegate electrode G, however, in the alignment mark formation region, thepattern P2 is not formed in the same layer as that of the gate electrodeG, and therefore, the silicon oxide film 8 is formed over thesemiconductor substrate 1S. This means that the roughness of afoundation that forms the silicon oxide film differs considerablybetween the integrated circuit formation region and the alignment markformation region. As a result, the flatness of the silicon oxide film 8formed in the alignment mark formation region is degraded. Similarly, inthe integrated circuit formation region, the first layer wiring L1 isformed, however, in the alignment mark formation region, the pattern(pattern P1 b) corresponding to the first layer wiring L1 is not formed,and therefore, the flatness of the silicon oxide film 9 formed in thealignment mark formation region is also degraded. Further, in theintegrated circuit formation region, the second layer wiring L2 isformed, however, in the alignment mark formation region, the pattern(pattern P1 a) corresponding to the second layer wiring L2 is notformed, and therefore, the flatness of the silicon oxide film 10 formedin the alignment mark formation region is also degraded. That is, whenthe foundation pattern is even, the flatness of the film formed over thefoundation pattern is excellent, however, if the foundation pattern isnot even, the flatness of the film formed on the foundation pattern isdegraded. From this, it is impossible to conclude that the flatness inthe alignment mark formation region is excellent. In the alignment markformation region, the mark MK1 is formed in the uppermost layer over theinterlayer insulating film, and therefore, if the flatness of theinterlayer insulating film formed in the lower layer of the mark MK1 isdegraded, the roughness of the interlayer insulating film is reflectedin the flatness of the mark MK1 and the flatness of the mark MK is alsodegraded. If the flatness of the mark MK1 is degraded, the travelingdirection of the light reflected from the mark MK1 varies. Consequently,when the light reflected from the mark MK1 is recognized with a cameraarranged in a specific direction, the amount of reflected light thattravels in the specific direction in which the camera is arrangedreduces. As a result, the difference between the reflected light fromthe mark MK1 that enters the camera and the reflected light from thebackground region becomes small and the difference in contrast betweenthe mark MK1 and the background region becomes small, resulting in thereduction in the visibility of the alignment mark with the camera. As aresult, the positioning precision of the semiconductor chip is degraded.

In contrast to this, in the first embodiment, the patterns P1 a, P1 b,P2, and P3 are formed in the lower layer of the mark MK1 formed in thealignment mark formation region. For example, in the alignment markformation region, the pattern P2 is formed in the same layer as that ofthe gate electrode G formed in the integrated circuit formation region,and therefore, the pattern of the foundation film by the gate electrodeG and the pattern P2 becomes even and it is possible to improve theflatness of the silicon oxide film 8 formed on the gate electrode G andthe pattern P2. Similarly, in the alignment mark formation region, thepattern P1 b is formed in the same layer as that of the first layerwiring L1 formed in the integrated circuit formation region and further,the pattern P1 a is formed in the same layer as that of the second layerwiring L2, and therefore, it is possible to improve the flatness of thesilicon oxide film 9 and the silicon oxide film 10. From this, theflatness of the mark MK1 can also be improved because the flatness ofthe foundation film formed in the lower layer of the mark MK1 isimproved in the alignment mark formation region. As a result, the lightreflected from the mark MK1 travels all together in the specificdirection, and therefore, by arranging the camera in the specificdirection, it is possible to suppress the amount of light reflected fromthe mark MK1 from reducing. Consequently, the difference between thereflected light from the mark MK1 that enters the camera and thereflected light from the background region becomes large and thedifference in contrast between the mark MK1 and the background region isimproved. Consequently, it is possible to suppress the visibility of thealignment mark with a camera from reducing and improve the positioningprecision of a semiconductor chip.

In particular, in the first embodiment, the arrangement of the patternsP1 a, P1 b, P2 and P3 also immediately under the mark MK1 functionseffectively. For example, from the standpoint of the first mechanism andthe second mechanism, it is possible to obtain the effect that theamount of light reflected from the background region can be reduced onlyby providing the patterns P1 a, P1 b, P2, and P3 immediately under thebackground region. In contrast to this, from the standpoint of the thirdmechanism that improves the flatness of the mark MK1, the formation ofthe pattern equivalent to the pattern formed in the integrated circuitformation region immediately under the mark MK1 has a meaning. With sucha configuration, it is possible to improve the flatness of thefoundation film formed immediately under the mark MK1 and therefore toimprove the flatness of the mark MK1. That is, from the standpoint ofthe third mechanism, by forming the patterns P1 a, P1 b, P2 and P3immediately under the mark MK1 in the alignment mark formation region,it is possible to obtain the remarkable effect that the flatness of themark MK1 can be improved.

From the above, in the first embodiment, it is possible to make largethe difference in contrast of the alignment mark by means of the firstmechanism that makes use of the diffraction and interference of light,the second mechanism that makes use of the scattering and cut off oflight, and the third mechanism that makes use of the evenness of thefoundation pattern. Consequently, the visibility of the alignment markis improved and the positioning precision of a semiconductor chip can beimproved. That is, in the first embodiment, even if the difference incontrast of the alignment mark varies for each semiconductor chip, it ispossible to obtain a difference in contrast that overcomes thevariations. From this, it is possible to improve the visibility of thealignment mark and improve the positioning precision of anysemiconductor chip even if the semiconductor chip is obtained from adifferent semiconductor wafer or the semiconductor chip is obtained froma difference chip region of the same semiconductor chip.

Next, the difference between the technical idea in the first embodimentand the technique described in the documents of the prior art describedin “BACKGROUND OF THE INVENTION” will be described.

In patent document 1 (Japanese patent laid-open No. 11-330247), atechnique is described, which is capable of accurately detecting analignment mark when forming an alignment mark for laser trimming withina chip. Specifically, over the surface of a semiconductor substrate madeof an SOI substrate, there is provided a tapered part oblique withrespect to the normal direction at least in the peripheral region of thealignment mark and laser light is bound to be reflected in a directiondifferent from the normal direction at the tapered part. As a result, itis possible to reduce the reflection of laser light in the normaldirection of the semiconductor substrate in the peripheral region of thealignment mark, and therefore, it is possible to accurately distinguishthe alignment mark from its peripheral region. Consequently, it isconcluded that the detection of an alignment mark can be carried outaccurately also when forming an alignment mark within a chip. In thiscase, the tapered part is formed in the same layer as that of theelement isolation region formed in the semiconductor substrate. Inpatent document 1, the element isolation region is formed by LOCOS(Local Oxidation of Silicon) and the pattern similar to LOCOS is formedalso in the peripheral region of the alignment mark. Then, it ispossible to shift the reflection direction of laser light from thenormal direction of the semiconductor substrate by making use of thefact that there are tapered parts on both ends of LOCOS. As a result,according to the technique described in patent document 1, it ispossible to improve the detection accuracy of alignment mark byirradiating laser light to the semiconductor substrate and based on thedifference in intensity between light reflected from the alignment markand light reflected from the background region (peripheral region of thealignment mark). This technique is premised on the incidence of laserlight and if, for example, general lighting with a xenon lamp, which hasa random direction, is used, the effect is reduced. That is, with axenon lamp, the direction of incident light is random, and therefore,the reflected light is also output in a random direction. In this case,even if the tapered part is provided over the main surface of thesemiconductor substrate, incident light in a ransom direction is justconverted into reflected light in a random direction, and therefore, theeffect of the provision of the tapered part is small. The techniquedescribed in patent document 1 is a technique that can be applied to thecase where laser light incident to the semiconductor substrate in thenormal direction is reflected in the normal direction of thesemiconductor substrate.

In contrast to this, the technical idea described in the firstembodiment provides the patterns P1 a, P1 b, P2 and P3 across aplurality of layers in the lower layer of the mark MK1 and thebackground region formed in the alignment mark formation region.Consequently, the effect can be obtained by the first mechanism thatmakes use of diffraction and interference of light. This function is notdescribed nor suggested in the technique described in patent document 1.In particular, in patent document, only the tapered part is provided andthe technique is effective only when the semiconductor substrate isirradiated with laser light in the normal direction. On the other hand,in the first embodiment, the effect can be obtained when not only laserlight but also a xenon lamp having an incident light of random directionis used. According to the configuration in the first embodiment, evenwhen a xenon lamp is used, it is possible to reduce reflected light fromthe background region due to the first mechanism because the phenomenonof diffraction and interference of light occurs.

Further, by providing the patterns P1 a, P1 b in the same layer as thatof the wiring layer of the integrated circuit formation region, thesecond mechanism is realized that makes use of the cut off effect oflight besides the diffraction and interference of light described above.The cut off effect of light is not described nor suggested in patentdocument 1. In particular, by providing the pattern P2 in the same layeras that of the gate electrode G and the pattern P3 in the same layer asthat of the element isolation region STI as well as providing thepatterns P1 a, P1 b in the same layer as that of the wiring layer in theintegrated circuit formation region, scattering of light over the mainsurface of the semiconductor substrate 1S is also made use of. That is,there is an advantage that the cut off effect of reflected light by thepatterns P1 a, P1 b can be improved by making use of scattering of lightover the main surface of the semiconductor substrate 1S. This point isalso not described nor suggested in patent document 1.

In the third embodiment, it is possible to improve flatness of the markMK1 due to the third mechanism, and also from this standpoint, it isconcluded that the visibility of alignment mark can be improved. Incontrast to this, in patent document 1, the flatness of alignment markis not described nor suggested.

From the above, the characteristic of the first embodiment that thevisibility of alignment mark can be improved by the first mechanism thatmakes use of diffraction and interference of light, the second mechanismthat makes use of scattering of light and cut off of light, and thethird mechanism that makes use of the evenness of the foundation patternis not described nor suggested in patent document 1 and there is nodescription that will motivate the thinking of the technical idea of thefirst embodiment. Therefore, it can be thought that it is difficult foreven a person skilled in the art to hit on the technical idea of thefirst embodiment from the technique described in patent document 1.

Subsequently, the difference in technical idea between patent document 2(Japanese patent laid-open No. 2000-182914) and the first embodimentwill be described. In patent document 2, a diffusion reflection layermade of aluminum is formed in the peripheral region of a cross-shapedmark main body part formed as a solid pattern of an aluminum layer. Itdescribes that as a diffusion reflection layer, for example, astripe-shaped, grating-shaped, or dot-shaped fine pattern formed by analuminum layer can be used. In this case, the diffusion reflection layerformed in the peripheral region of the cross-shaped mark main body partis formed in the same layer as that of the mark main body part.

The technique described in patent document 2, forms the diffusionreflection layer in the peripheral region in the same layer as that ofthe mark main body part and reduces the reflected light from thediffusion reflection layer due to scattering and interference of lightby the diffusion reflection layer.

In contrast to this, in the first embodiment, the different point isthat the patterns P1 a, P1 b, P2 and P3 are provided in the lower layerof the mark MK1 and the background region, not in the same layer as thatof the mark MK1 and the background region. As described above, the firstembodiment is characterized by providing the patterns P1 a, P1 b, P2 andP3 in the lower layer of the mark MK1 and the background region and thefirst embodiment brings about the remarkable effect that cannot beobtained from the configuration in patent document 2 in which thediffusion reflection layer is formed in the same layer as that of themark main body part.

This point will be described. Firstly, in the semiconductor chip, whichis the LCD driver, the alignment mark is formed for positioning. Thealignment mark is formed by the mark and the background regionsurrounding the mark. According to the general specifications ofalignment mark, nothing is formed in the background region in the samelayer as that of the mark. This is to improve the visibility of the markitself and prevent the possibility of degradation of visibility if anexcessive pattern is formed in the background region in the same layeras that of the mark. As a result, the technique as described in patentdocument 2, in which the diffusion reflection layer is formed in thesame layer as that of the mark main body part, does not satisfy thespecifications, and therefore, it cannot be a practical configurationfrom the standpoint of satisfying the specifications. On the other hand,in the first embodiment, nothing is formed in the same layer as that ofthe mark MK1 and the patterns P1 a, P1 b, P2 and P3 are formed in thelower layer of the mark MK1 and the background region. In this case,nothing is formed in the background region in the same layer as that ofthe mark MK1, and therefore, the configuration in the first embodimentsatisfies the specifications unlike patent document 2.

Secondly, in patent document 2, the diffusion reflection layer is formedin the same layer as that of the mark main body part. The mark main bodypart is formed by the uppermost layer wiring and the diffusionreflection layer formed in the same layer as that of the mark main bodypart is also formed by the uppermost layer wiring. In general, however,the film thickness of the uppermost layer wiring is much greater thanthat of the wiring in other layers and it is difficult to fine processthe thick uppermost layer wiring. That is, in patent document 2, thediffusion reflection layer composed of the grating-shaped or dot-shapedfine pattern is formed in the same layer as that of the mark main bodypart, however, the diffusion reflection layer is formed by processingthe uppermost layer wiring, and therefore, it is difficult to fineprocess the uppermost layer wiring so as to sufficiently realizescattering and interference of light. In contrast to this, in the firstembodiment, instead of the uppermost layer wiring, a wiring thin in filmthickness formed in the lower layer than the uppermost layer wiring isused and processed, and therefore, it is possible to easily form a finepattern having intervals of the size of visible light.

Thirdly, in patent document 2, the diffusion reflection layer is formedin the uppermost layer of the wiring layer, and therefore, the residualratio of the metal film in the uppermost layer increases. That is, ifthe diffusion reflection layer is not formed, only the mark main bodypart is formed in the uppermost layer of the wiring in the alignmentmark formation region, as a result. In contrast to this, in patentdocument 2, the diffusion reflection layer made of metal film is formedin the same layer as that of the mark main body part, and therefore, thecoating rate of the metal film increases. The mark main body part andthe diffusion reflection layer are formed by the normal patterning andin the normal patterning, etching of the metal film is carried out. Inthe etching, detection of an endpoint is carried out with plasma lightemission. That is, by etching a formed metal film, the mark main bodypart and the diffusion reflection layer are processed. At this time,when the diffusion reflection layer is formed, the more metal film iscaused to remain corresponding to the amount of the formation of thediffusion reflection layer. In other words, the unwanted metal film isremoved by etching, however, the diffusion reflection layer is formed,and accordingly, the region of etching is reduced.

During the period of etching, the product due to the etching is abundantin quantity and the intensity of light emission from the product ishigh. In contrast to this, in the vicinity of the endpoint of theetching, the product due to the etching decreases in quantity andtherefore the intensity of light emission from the product becomessmall. By monitoring the difference in light emission intensity from theproduct, the endpoint is detected. That is, it is possible to detect theendpoint of the etching by making use of the fact that the difference inlight emission intensity from the product due to the etching becomeslarge.

However, when the diffusion reflection layer is formed, the area of theregion of etching decreases, and therefore, the intensity of lightemission from the product becomes small even during the period ofetching. This means that the difference in light emission intensity bythe product becomes small between during the period of etching and nearthe endpoint of the etching. If the difference in light emissionintensity of the product becomes small, it becomes difficult to detectthe endpoint of the etching. That is, if the residual ratio of metalfilm in the uppermost layer increases due to the formation of thediffusion reflection layer, the possibility is increased that thedetection of the endpoint of the etching for processing the mark mainbody part and the diffusion reflection layer cannot be carried outaccurately. If the accurate detection of the endpoint of the etchingbecomes difficult to carry out, there arise problems of poor processingdue to the incompleteness of the etching, and the reduction in processeddimensions due to over-etching, etc. Consequently, from the standpointof the execution of the accurate processing of the mark main body partformed in the uppermost layer, it can be seen that it is desirable notto form the diffusion reflection layer of metal film in the same layeras that of the mark main body part. As to this point, in the firstembodiment, no pattern is formed in the background region in the samelayer as that of the mark, and therefore, the above-mentioned problemscan be avoided. As a result, there is an advantage that an attempt canbe made to improve the processing precision of the mark that will resultin the improvement of the visibility of alignment mark.

Fourthly, the characteristic of the first embodiment that the visibilityof alignment mark can be improved by the first mechanism that makes useof diffraction and interference of light, the second mechanism thatmakes use of scattering of light and cut off of light, and the thirdmechanism that makes use of the evenness of the foundation pattern isnot described nor suggested in patent document 2 and there is nodescription that will motivate the thinking of the technical idea of thefirst embodiment. From the above, it can be thought that it is difficultfor even a person skilled in the art to hit on the technical idea of thefirst embodiment from the technique described in patent document 2.

The semiconductor device in the first embodiment is configured asdescribed above, and the method of manufacturing the same will bedescribed below with reference to the drawings. The configuration of thesemiconductor device in the first embodiment is shown as those in FIG. 6to FIG. 8, however, for the sake of simple explanation, a configurationin FIG. 9 is also formed, which is a combination of those in FIG. 7 andFIG. 8. In the method of manufacturing the semiconductor device in thefirst embodiment, a section view corresponding to FIG. 9 is used forexplanation in order to make easier-to-see the positional relationshipbetween the patterns P1 a, P1 b, P2 and P3 formed in the alignment markformation region.

First, as shown in FIG. 11, the semiconductor substrate 1S made ofsilicon single crystal into which p-type impurities such as boron (B)have been introduced is prepared. In this case, the semiconductorsubstrate 1S is in the state of a semiconductor wafer in the shape ofsubstantially a circular disc. Then, as shown in FIG. 12, the elementisolation region STI that isolates the elements is formed in theintegrated circuit formation region of the semiconductor substrate 1S isformed. The element isolation region STI is formed to prevent theelements from interfering with each other. The element isolation regionSTI can be formed using, for example, the STI (Shallow trench isolation)method. For example, by the STI method, the element isolation region STIis formed as follows. That is, an element isolation groove is formed onthe semiconductor substrate 1S by using the photolithography techniqueand the etching technique. Then, a silicon oxide film is formed over thesemiconductor substrate 1S so as to be embedded in the element isolationgroove. After that, by the CMP (chemical mechanical polishing) method,the unwanted silicon oxide film formed over the semiconductor substrate1S is removed. Consequently, it is possible to form the elementisolation region STI in which the silicon oxide film is embedded only inthe element isolation groove. In the first embodiment, in the processfor forming the element isolation region STI in the integrated circuitformation region, the element isolation region STI is formed also in theguard ring region and the pattern P3 is formed also in the alignmentmark formation region. The pattern P3 formed in the alignment markformation region also has a structure in which the silicon oxide film isembedded in the groove similar to the element isolation region STIformed in the integrated circuit formation region. In the firstembodiment, one of the characteristics is that the pattern P3 is formedin the alignment mark formation region and it is possible to simplifythe process by forming the pattern P3 in the same process as that of theelement isolation region STI.

Next, the p-type well PWL is formed by introducing impurities into theactive region of the integrated circuit formation region isolated by theelement isolation region STI. The p-type well PWL is formed byintroducing p-type impurities such as boron into the semiconductorsubstrate 1S by the ion implantation method.

Subsequently, a semiconductor region (not shown) for forming a channelis formed in the surface region of the p-type well PWL. The channelformation semiconductor region is formed in order to adjust a thresholdvoltage that forms a channel.

Next, as shown in FIG. 13, the gate insulating film 2 is formed over thesemiconductor substrate 1S. The gate insulating film 2 is formed by, forexample, a silicon oxide film and can be formed by using, for example,the thermal oxidation method. However, the gate insulating film 2 is notlimited to the silicon oxide film but there can be various modificationsand, for example, the gate insulating film 2 may be formed by a siliconoxynitride film (SiON). That is, the structure may be one in whichnitrogen is segregated in the boundary face between the gate insulatingfilm 2 and the semiconductor substrate 1S. The silicon oxynitride filmis more effective than the silicon oxide film in suppressing theoccurrence of boundary face level in the film and in reducing theelectron trap. Consequently, it is possible to improve the hot carrierresistant property and the insulating property of the gate insulatingfilm 2. The silicon oxynitride film is more difficult for impurities topenetrate, through compared to the silicon oxide film. Consequently, byusing the silicon oxynitride film as the gate insulating film 2, it ispossible to suppress the variations in the threshold voltage resultingfrom the diffusion of impurities in the gate electrode toward the sideof the semiconductor substrate. The silicon oxynitride film can beformed by subjecting the semiconductor substrate 1S to a heat treatmentin an atmosphere of NO, NO₂, or NH₃, which includes nitrogen. It is alsopossible to obtain the same effect by, after forming the gate insulatingfilm 2 made of silicon oxide film over the surface of the semiconductorsubstrate 1S, subjecting the semiconductor substrate 1S to a heattreatment in an atmosphere including nitrogen and segregating nitrogenin the boundary face between the gate insulating film 2 and thesemiconductor substrate 1S.

The gate insulating film 2 may also be formed by, for example, a highdielectric constant film having a higher dielectric constant than thatof the silicon oxide film. Conventionally, the silicon oxide film isused as the gate insulating film 2 from the standpoint of the fact thatthe insulating property is excellent and the electric/physical stabilityin the boundary surface between silicon and silicon oxide is excellent.However, as miniaturization of elements advances, the film thickness ofthe gate insulating film 2 is demanded to be extremely thin. If such athin silicon oxide film is used as the gate insulating film 2, theelectrons that flow through the MISFET channel penetrate through thebarrier wall formed by the silicon oxide film to the gate electrode,that is, a so-called tunnel current occurs.

Therefore, recently, a high dielectric film comes to be used, which canincrease a physical film thickness even with the same capacitance by useof a material having a higher dielectric constant than that of a siliconoxide film. The high dielectric constant film makes it possible toincrease the physical film thickness while maintaining its capacitanceunchanged, thereby reducing leak current.

For example, as a high dielectric film, a hafnium oxide film (HfO₂ film)is used, which is one of hafnium oxides. However, instead of the hafniumoxide film, other hafnium-based insulating films such as hafniumaluminate film, HfON film (hafnium oxynitride film), HfSiO film (hafniumsilicate film), HfSiON film (hafnium silicon oxynitride film), and HfAlOfilm, can be used. Further, hafnium-based insulating films that haveintroduced oxides therein, such as tantalum oxide, niobium oxide,titanium oxide, zirconium oxide, lanthanum oxide, and yttrium oxide, canalso be used. Since the hafnium-based insulating film has a higherdielectric constant than that of the silicon oxide film and the siliconoxynitride film, like the hafnium oxide film, the same effect when thehafnium oxide film is used can be obtained.

Subsequently, the polysilicon film 3 is formed over the gate insulatingfilm 2. The polysilicon film 3 can be formed by using, for example, theCVD method. Then, n-type impurities such as phosphorus and arsenic areintroduced into the polysilicon film 3 formed in the n-channel typeMISFET formation region by using the photolithography technique and theion implantation method.

Next, as shown in FIG. 14, the gate electrode G is formed in theintegrated circuit formation region by processing the polysilicon film 3by etching using a patterned resist film as a mask. With thispatterning, the pattern P2 formed in the same layer as that of the gateelectrode G is formed in the alignment mark formation region. One of thecharacteristics of the first embodiment is that the pattern P2 is formedin the alignment mark formation region and the process can be simplifiedby forming the pattern P2 in the same process as that of the gateelectrode G.

Here, in the gate electrode G in the integrated circuit formationregion, n-type impurities have been introduced into the polysilicon film3. Consequently, the work function value of the gate electrode G can beset to a value in the vicinity of the conduction band of silicon (4.15eV), and therefore, it is possible to reduce the threshold voltage ofthe n-channel type MISFET.

Subsequently, as shown in FIG. 15, the low concentration n-type impuritydiffusion region 4, which is shallow and consistent with the gateelectrode G of the n-channel type MISFET, is formed by using thephotolithography technique and the ion implantation method. The shallowlow concentration n-type impurity diffusion region 4 is a semiconductorregion.

Next, a silicon oxide film is formed over the semiconductor substrate1S. The silicon oxide film can be formed by, for example, using the CVDmethod. Then, the sidewall 5 is formed on the sidewall of the gateelectrode G by anisotropic etching of the silicon oxide film. Thesidewall 5 is formed from a single layer film of the silicon oxide film,however, this is not limited and, for example, a sidewall made up of alaminated film of silicon nitride film and silicon oxide film may beformed.

Subsequently, the high concentration n-type impurity diffusion region 6,which is deep and consistent with the sidewall 5, is formed in then-channel type MISFET formation region using the photolithographytechnique and the ion implantation method. The deep high concentrationn-type impurity diffusion region 6 is a semiconductor region. The deephigh concentration n-type impurity diffusion region 6 and the shallowlow concentration n-type impurity diffusion region 4 together form thesource region. Similarly, the deep high concentration n-type impuritydiffusion region 6 and the shallow low concentration n-type impuritydiffusion region 4 together form the drain region. By forming the sourceregion and the drain region by the shallow n-type impurity diffusionregion 4 and the deep n-type impurity diffusion region 6 in this manner,it is possible to let the source region and the drain region have theLDD (Lightly Doped Drain) structure.

After forming the deep high concentration n-type impurity diffusionregion 6 as described above, a heat treatment at about 1,000° C. iscarried out. Consequently, the introduced impurities are activated.

After that, although not shown schematically, for example, a cobalt filmis formed over the semiconductor substrate′. At this time, the cobaltfilm is formed so as to directly touch the gate electrode G. Similarly,the cobalt film directly touches also the deep high concentration n-typeimpurity diffusion region 6.

The cobalt film can be formed using, for example, the sputtering method.After forming the cobalt film and subjecting it to a heat treatment, thepolysilicon film 3 constituting the gate electrode G and the cobalt filmare caused to react with each other to form a cobalt silicide film (notshown). Consequently, the gate electrode G has a laminated structure ofthe polysilicon film 3 and the cobalt silicide film (not shown). Thecobalt silicide film (not shown) is formed in order to reduce theresistance of the gate electrode G. Similarly, by the above-mentionedheat treatment, silicon and the cobalt film react with each other alsoover the surface of the deep high concentration n-type impuritydiffusion region 6 and the cobalt silicide film (not shown) is formed.As a result, it is possible to reduce the resistance also in the deephigh concentration n-type impurity diffusion region 6.

Then, the unreacted cobalt film is removed from the semiconductorsubstrate 1S. In the first embodiment, the cobalt silicide film (notshown) is formed, however, instead of the cobalt silicide film (notshown), a nickel silicide film or titanium silicide film may be formed.

Next, as shown in FIG. 16, over the main surface of the semiconductorsubstrate 1S, the silicon nitride film 7, which serves as an interlayerinsulating film, is formed. The silicon nitride film 7 can be formed by,for example, the CVD method, and is a film formed to form a contact holeto be formed in the later process by self-align (SAC). Then, as shown inFIG. 17, the silicon oxide film 8, which serves as an interlayerinsulating film, is formed over the silicon nitride film. 7. The siliconoxide film 8 can be formed using the CVD method with, for example, TEOS(tetra ethyl ortho silicate) as a raw material. Then, the surface of thesilicon oxide film 8 is flattened by using, for example, the CMP(Chemical Mechanical Polishing) method. At this time, in the lower layerof the silicon oxide film 8, which is an interlayer insulating film, thepattern P2 is also formed besides the gate electrode G. Consequently,the foundation pattern (gate electrode G and pattern P2) of the siliconoxide film 8 is even from the integrated circuit formation region to thealignment mark formation region, and therefore, the flatness of thesilicon oxide film 8 is improved in the alignment mark formation region.

Subsequently, a contact hole is formed in the silicon oxide film 8 usingthe photolithography technique and the etching technique. Then, atitanium/titanium nitride film is formed over the silicon oxide filmincluding the bottom and inner wall of the contact hole. Thetitanium/titanium nitride film is made up of a laminated film oftitanium film and titanium nitride film and can be formed by using, forexample, the sputtering method. The titanium/titanium nitride film has aso-called barrier property that prevents, for example, tungsten, whichis a material of a film to be embedded in a later process, fromdiffusing into silicon. Then, a tungsten film is formed over the entiremain surface of the semiconductor substrate 1S so as to be embedded inthe contact hole. The tungsten film can be formed by using, for example,the CVD method. Then, the plug PLG1 can be formed by removing theunwanted titanium/titanium nitride film and the tungsten film formedover the silicon oxide film 8 by, for example, the CMP method. The plugPLG1 is formed in, for example, the integrated circuit formation regionand the guard ring region.

Next, as shown in FIG. 18, a titanium/titanium nitride film, an aluminumfilm containing copper and a titanium/titanium nitride film are formedsequentially over the silicon oxide film 8 and the plug PLG1. Thesefilms can be formed by using, for example, the sputtering method.Subsequently, these films are patterned by using the photolithographytechnique and the etching technique and the first layer wiring L1 isformed. In this process, the wiring GR1 is formed in the guard ringregion and the pattern P1 b is formed in the alignment mark formationregion. One of the characteristics of the first embodiment is that thepattern P1 b is formed in the alignment mark formation region and theprocess can be simplified by forming the pattern P1 b in the sameprocess as that of the first layer wiring L1. The pattern P1 b is formedwith the same pattern as that of the pattern P2 formed in the lowerlayer and the pattern P1 b is formed so as to overlap the pattern P2 ina planar manner.

Subsequently, as shown in FIG. 19, the silicon oxide film 9 is formedover the silicon oxide film 8 as well as over the first layer wiring L1,the pattern P1 b, and the wiring GR1. The silicon oxide film 9 can beformed by using the CVD method with, for example, TEOS (tetra ethylortho silicate) as a raw material. Then, the surface of the siliconoxide film 9 is flattened by using, for example, the CMP (ChemicalMechanical Polishing) method. At this time, in the lower layer of thesilicon oxide film 9, which is an interlayer insulating film, thepattern P1 b is also formed besides the first layer wiring L1.Consequently, the foundation pattern (the first layer wiring L1 and thepattern P1 b) of the silicon oxide film 9 is even from the integratedcircuit formation region to the alignment mark formation region, andtherefore, the flatness of the silicon oxide film 9 is improved in thealignment mark formation region.

Subsequently, a contact hole is formed in the silicon oxide film 9 usingthe photolithography technique and the etching technique. Then, atitanium/titanium nitride film is formed over the silicon oxide filmincluding the bottom and inner wall of the contact hole. Thetitanium/titanium nitride film is made up of a laminated film oftitanium film and titanium nitride film and can be form by using, forexample, the sputtering method. The titanium/titanium nitride film has aso-called barrier property that prevents, for example, tungsten, whichis a material of a film to be embedded in a later process, fromdiffusing into silicon. Then, a tungsten film is formed over the entiremain surface of the silicon oxide film 9 so as to be embedded in thecontact hole. The tungsten film can be formed by using, for example, theCVD method. Then, the plug PLG2 can be formed by removing the unwantedtitanium/titanium nitride film and the tungsten film formed on thesilicon oxide film 9 by, for example, the CMP method. The plug PLG2 isformed in, for example, the integrated circuit formation region and theguard ring region.

Next, as shown in FIG. 20, a titanium/titanium nitride film, an aluminumfilm containing copper and a titanium/titanium nitride film are formedsequentially over the silicon oxide film 9 and the plug PLG2. Thesefilms can be formed by using, for example, the sputtering method.Subsequently, these films are patterned by using the photolithographytechnique and the etching technique and the second layer wiring L2 isformed. In this process, the wiring GR2 is formed in the guard ringregion and the pattern P1 a is formed in the alignment mark formationregion. One of the characteristics of the first embodiment is that thepattern P1 a is formed in the alignment mark formation region and theprocess can be simplified by forming the pattern P1 a in the sameprocess as that of the second layer wiring L2. The pattern P1 a isformed with a pattern shifted from that of the pattern P2 formed in thelower layer and the pattern P1 a is formed so as not to overlap thepattern P1 b in a planar manner.

Subsequently, as shown in FIG. 21, the silicon oxide film 10 is formedover the silicon oxide film 9 as well as over the second layer wiringL2, the pattern P1 a, and the wiring GR2. The silicon oxide film 10 canbe formed by using the CVD method with, for example, TEOS (tetra ethylortho silicate) as a raw material. Then, the surface of the siliconoxide film 10 is flattened by using, for example, the CMP (ChemicalMechanical Polishing) method. At this time, in the lower layer of thesilicon oxide film 10, which is an interlayer insulating film, thepattern P1 a is also formed besides the second layer wiring L2.Consequently, the foundation pattern (the second layer wiring L2 and thepattern P1 a) of the silicon oxide film 10 is even from the integratedcircuit formation region to the alignment mark formation region, andtherefore, the flatness of the silicon oxide film 10 is improved in thealignment mark formation region.

Subsequently, a contact hole is formed in the silicon oxide film 10using the photolithography technique and the etching technique. Then, atitanium/titanium nitride film is formed over the silicon oxide filmincluding the bottom and inner wall of the contact hole. Thetitanium/titanium nitride film is made up of a laminated film oftitanium film and titanium nitride film and can be formed by using, forexample, the sputtering method. The titanium/titanium nitride film has aso-called barrier property that prevents, for example, tungsten, whichis a material of a film to be embedded in a later process, fromdiffusing into silicon. Then, a tungsten film is formed over the entiresurface of the silicon oxide film 10 so as to be embedded in the contacthole. The tungsten film can be formed by using, for example, the CVDmethod. Then, the plug PLG3 can be formed by removing the unwantedtitanium/titanium nitride film and the tungsten film formed over thesilicon oxide film 10 by, for example, the CMP method. The plug PLG3 isformed in, for example, the integrated circuit formation region and theguard ring region.

Next, a titanium/titanium nitride film, an aluminum film containingcopper, and a titanium/titanium nitride film are formed sequentiallyover the silicon oxide film 10 and the plug PLG3. These films can beformed by using, for example, the sputtering method. Subsequently, thesefilms are patterned by using the photolithography technique and theetching technique and the third layer wiring L3 is formed. In thisprocess, the wiring GR3 is formed in the guard ring region and the markMK1 is formed in the alignment mark formation region. In the alignmentmark formation region, the patterns P1 a, P1 b, P2, and P3 are arrangedin the lower layer of the mark MK1 and the background region surroundingthe mark MK1. In the manner described above, it is possible to form theMISFET and the multilayer wiring in the integrated circuit formationregion of the semiconductor substrate 1S and to form the patterns P1 a,P1 b, P2 and P3 and the mark MK 1 in the alignment mark formationregion. Further, it is possible to form a guard ring structure in theguard ring region.

Next, the process for forming a bump electrode in the integrated circuitformation region will be described. First, as shown in FIG. 22, thesilicon oxide film 11 is formed over the silicon oxide film 10 as wellas over the third layer wiring L3, the mark MK 1 and the wiring GR3, andover the silicon oxide film 11 the silicon nitride film 12 is formed.The silicon oxide film 11 and the silicon nitride film 12 can be formedby, for example, the plasma CVD method. In this manner, it is possibleto form a surface protection film made up of the silicon oxide film 11and the silicon nitride film 12 over the uppermost layer wiring layer(the third layer wiring L3).

Subsequently, the opening 13 is formed in the surface protection filmusing the photolithography technique and the etching technique. Theopening 13 is formed over the third layer wiring L3 (pad), exposing thesurface of the third layer wiring L3. The opening 13 is formed so thatits size is smaller than that of the third layer wiring L3 (pad).

Next, as shown in FIG. 23, the UBM (Under Bump Metal) film 14 is formedover the surface protection film including the interior of the opening13. The UBM film 14 can be formed by using, for example, the sputteringmethod and is formed by a single layer film or laminated film of such astitanium film, nickel film, palladium film, titanium/tungsten alloyfilm, titanium nitride film, and gold film. The UBM film 14 is a filmhaving the barrier function to move metal elements of a gold film to beformed in the later process, to the third layer wiring L3 etc. and tosuppress or prevent, on the contrary, the metal elements of the thirdlayer wiring 3 etc. from moving toward the side of the gold film,besides the function to improve adhesion between the bump electrode andthe pad or the surface protection film.

Subsequently, after applying a resist film 15 over the UBM film 14, theresist film 15 is subjected to the exposure/development process and thuspatterned. The patterning is carried out so that an opening 16 is formedwithout the resist film 15 being left in the bump electrode formationregion. Then, as shown in FIG. 24, the gold film 17 is formed within theopening 16 using the plating method. At this time, the gold film 17 isformed over the surface protection film (silicon nitride film 12) and isalso embedded in the opening 13. By embedding the gold film 17 in theopening 13, the plug is formed.

After that, by removing the patterned resist film 15 and the UBM film 14covered with the resist film 15, the bump electrode BP1 made up of thegold film 17 and the UBM film as shown in FIG. 9 is formed. Then, bydicing the semiconductor substrate 1S, the semiconductor chip CHP intowhich the semiconductor substrate 1S is divided can be obtained.

Next, the process for adhering and mounting the semiconductor chip CHPformed as above in a mounting substrate will be described. FIG. 25 showsthe case where the semiconductor chip CHP is mounted over a glasssubstrate 20 (COG: Chip On Glass). As shown in FIG. 25, over the glasssubstrate 20, a glass substrate 21 is mounted and thus the display partof the LCD is formed. Then, over the glass substrate 20 in the vicinityof the display part of the LCD, there is a region in which thesemiconductor chip CHP, which is the LCD driver, is to be mounted. Inthe semiconductor chip CHP the bump electrodes BP1, BP2 are formed andthe bump electrodes BP1, BP2 and an electrode 20 a (ITO electrode)formed over the glass substrate 20 are coupled via an anisotropicconductive film ACF. The anisotropic conductive film ACF is configuredso as to have an insulating layer 22 and metal particles 23.

In this process, the positioning of the semiconductor chip CHP and theelectrode 20 a formed over the glass substrate 20 is carried out using acamera C. In this positioning, by recognizing the alignment mark formedin the semiconductor chip CHP with the camera C, the accurate positionof the semiconductor chip CHP is grasped. In the first embodiment, it ispossible to make large enough the difference in contrast between themark of the alignment mark and the background region surrounding themark, and therefore, the visibility of the alignment mark with thecamera C can be improved. Consequently, it is possible to carry outaccurate positioning between the bump electrodes BP1, BP2 formed in thesemiconductor chip CHP and the electrodes 20 a formed over the glasssubstrate 20.

FIG. 26 is a section view showing how the semiconductor chip CHP ismounted over the anisotropic conductive film ACF after the positioningwith the camera C. In this case, because of the accurate positioningbetween the semiconductor chip CHP and the glass substrate 20, the bumpelectrodes BP1, BP2 are positioned over the electrodes 20 a.

Subsequently, as shown in FIG. 27, the bump electrodes BP1, BP2 and theterminals 20 a are coupled through the anisotropic conductive film ACF.The anisotropic conductive film ACF is a film formed into a film shapeby mixing conductive fine metal particles with a thermosetting resin.The metal particle is mainly made up of a ball having a diameter of 3 to5 μm, inside of which a nickel layer and a gold plating layer are formedand the outermost of which is overlapped with an insulating layer. Inthis state, the anisotropic conductive film ACF is sandwiched betweenthe terminals 20 a of the glass substrate 20 and the bump electrodesBP1, BP2 of the semiconductor chip CHP when the semiconductor chip CHPis mounted in the glass substrate 20. Then, when a pressure is appliedto the semiconductor chip CHP while being heated using a heater etc.,the pressure is applied to only the regions corresponding to the bumpelectrodes BP1, BP2. Then, the metal particles dispersed in theanisotropic conductive film ACF touch and overlap each other, and thenare pressed against each other. As a result, a conductive path is formedin the anisotropic conductive film ACF via the metal particles. Themetal particles in the region of the anisotropic conductive film ACF towhich the pressure is not applied still have the insulating layer formedin the surface of the metal particle, and therefore, the insulationbetween the bump electrodes BP1 positioned side by side in the lateraldirection and between the bump electrodes BP2 positioned side by side inthe lateral direction can be maintained. Consequently, there is anadvantage that the semiconductor chip CHP can be mounted over the glasssubstrate 20 without causing short circuit even if the distances betweenthe bump electrodes BP1 and between the electrodes BP2 are small.

Subsequently, as shown in FIG. 28, the glass substrate 20 and a flexibleprinted circuit FPC are also coupled via the anisotropic conductive filmACF. In the semiconductor chip CHP mounted over the glass substrate 20in this manner, the bump electrode BP2 for output is electricallycoupled with the display part of the LCD and the bump electrode BP1 forinput is coupled with the flexible printed circuit FPC.

FIG. 29 is a diagram showing the entire configuration of an LCD (liquidcrystal display unit 25). As shown in FIG. 29, on the glass substrate, adisplay part 24 of the LCD is formed and on the display part 24, animage is displayed. On the glass substrate in the vicinity of thedisplay part 24, the semiconductor chip CHP, which is the LCD driver, ismounted. In the vicinity of the semiconductor chip CHP, the flexibleprinted circuit FPC is mounted and the semiconductor chip CHP, which isa driver, is mounted between the flexible printed circuit FPC and thedisplay part 24 of the LCD. In this manner, the semiconductor chip CHPcan be mounted on the glass substrate. As described above, it ispossible to mount the semiconductor chip CHP, which is an LCD driver, onthe liquid crystal display unit 25.

Second Embodiment

In the first embodiment described above, as shown in FIG. 7 and FIG. 8,the pattern P1 a and the pattern P3 formed in the different layers arearranged so that they overlap in a planar manner (refer to FIG. 7) andthe pattern P1 b and the pattern P2 formed in the different layers arearranged so that they overlap in a planar manner (refer to FIG. 8). Incontrast to this, in a second embodiment, an example will be described,in which the patterns P1 a, P1 b and P2 formed in the different layersare arranged so that they overlap in a planar manner but not overlap thepattern P3 in a planar manner.

FIG. 30 is a plan view showing a configuration of the alignment mark AMin the second embodiment. In the alignment mark AM in the secondembodiment, the cross-shaped mark MK1 is formed in the center of therectangular background region BG. Then, in the lower layer of thebackground region BG including the lower layer of the mark MK1, the dotpattern is formed. The dot pattern shown in FIG. 30 is formed across thelower layer of the mark MK1 and the lower layer of the background regionBG not in the same layer as that of the mark MK1. The dot pattern inFIG. 30 shows a pattern in which patterns formed across a plurality oflayers are overlapped in a planar manner not a pattern formed in thesame layer. For example, the dot pattern crossed by the A-A line in FIG.30 shows the pattern P3. That is, the A-A line in FIG. 30 is a line thatcuts the arrangement region of the pattern P3 constituting the dotpattern. On the other hand, the dot pattern crossed by the B-B line inFIG. 30 shows the pattern P1 a. Further, the dot pattern also shows thepattern P1 b, which is a planar pattern similar to the pattern P1 a,although formed in the different layer from that of the pattern P1 a.Furthermore, the dot pattern also shows the pattern P2, which is aplanar pattern similar to the pattern P1 b, although formed in thedifferent layer from that of the pattern P1 b. That is, the B-B line inFIG. 30 is a line that cuts the arrangement region of the patterns P1 a,P1 b, and the pattern P2 constituting the dot pattern. As describedabove, the dot pattern formed in the alignment mark AM in FIG. 30 isconfigured by alternately arranging the patterns (P3) on the A-A lineand the patterns (P1 a, P1 b, and P2) on the B-B line.

FIG. 31 is a section view cut by the A-A line in FIG. 30. It can be seenthat the pattern P3 is formed over the semiconductor substrate 1S in thealignment mark formation region, as shown in FIG. 31. The pattern P3 isformed in the same layer and the same structure as those of the elementisolation region STI formed in the integrated circuit formation region,as in the first embodiment.

FIG. 32 is a section view cut by the B-B line in FIG. 30. It can be seenthat the patterns P2, P1 b and P1 a are formed in the alignment markformation region, as shown in FIG. 32. Then it can also be seen that thepatterns P1 a, P1 b and P2 are formed in the different layers but formedso as to have the same pattern in a planar perspective.

FIG. 33 is a diagram in which FIG. 31 and FIG. 32 are overlapped. Withthe arrangement, the positional relationship between the patterns P1 a,P1 b, P2 and P3 is made easier-to-see. As shown in FIG. 33, the patternsP1 a, P1 b, P2 and P3 are formed in the lower layer of the mark MK1 andthe background region surrounding the mark MK1 and have the same patternin a planar perspective. On the other hand, the pattern P3 is arrangedso as to be shifted from the patterns P1 a, P1 b and P2, and the patternP3 is arranged so as not to overlap the patterns P1 a, P1 b and P2 in aplanar manner. As described above, in the second embodiment, thepatterns P1 b, P1 a, P2 and P3 are formed across the four layers as inthe first embodiment described above, however, the relationship ofplanar arrangement of the respective patters is different. Even in sucha case, the same effect as that in the first embodiment can be obtained.

That is, in the second embodiment also, it is possible to make large thedifference in contrast of the alignment mark by means of the firstmechanism that makes use of the diffraction and interference of light,the second mechanism that makes use of the scattering and cut off oflight, and the third mechanism that makes use of the evenness of thefoundation pattern. As a result, the visibility of the alignment mark isimproved and the positioning precision of a semiconductor chip can beimproved. That is, also in the second embodiment, even if the differencein contrast of the alignment varies for each semiconductor chip, it ispossible to obtain a difference in contrast that overcomes thevariations. From this, it is possible to improve the visibility of thealignment mark and improve the positioning precision of anysemiconductor chip even if the semiconductor chip is obtained from adifferent semiconductor wafer or the semiconductor chip is obtained froma different chip region of the same semiconductor chip.

As above, the invention made by the present inventors is describedspecifically based on the embodiments, however, it is obvious that thepresent invention is not limited to the above embodiments but variousmodifications can be made within the scope not departing from itsconcept.

The present invention can be used widely in the manufacturing industrythat manufactures semiconductor devices.

1-28. (canceled)
 29. A semiconductor device comprising: (1) a glasssubstrate having an electrode, and (2) a semiconductor chip disposed onthe glass substrate, the semiconductor chip including: (a) asemiconductor substrate including an alignment mark formation region andan integrated circuit formation region; (b) a MISFET formed over thesemiconductor substrate, the MISFET being formed in the integratedcircuit formation region; (c) a first wiring layer formed over theMISFET, the first wiring layer formed in the integrated circuitformation region; (d) a plurality of first patterns formed over thesemiconductor substrate and in the same layer as the first wiring layer,the plurality of first patterns being formed in the alignment markformation region; (e) a first interlayer insulating film formed over thesemiconductor substrate to cover the first wiring layer and theplurality of first patterns; (f) a second wiring layer formed over thefirst interlayer insulating film, the second wiring layer being formedin the integrated circuit formation region; (g) a plurality of secondpatterns formed over the first interlayer insulating film and in thesame layer as the second wiring layer, the plurality of second patternsbeing formed in the alignment mark formation region; (h) a secondinterlayer insulating film formed over the semiconductor substrate tocover the second wiring layer and the plurality of second patterns; (i)a third wiring layer formed over the second interlayer insulating film,the third wiring layer being formed in the integrated circuit formationregion; (j) an alignment mark formed over the second interlayerinsulating film and in the same layer as the third wiring layer, thealignment mark being formed in the alignment mark formation region; (k)a further insulating film formed over the semiconductor substrate tocover the third wiring and the alignment mark, the further insulatingfilm having an opening at an upper side of the third wiring layer; and(l) a bump electrode formed over the further insulating film andelectrically connected to the third wiring layer via the opening,wherein the plurality of first patterns and the plurality of secondpatterns are formed so as to be shifted from each other in a plan view,wherein the first wiring, the second wiring and the third wiring areelectrically connected to the MISFET, wherein the plurality of firstpatterns and the plurality of second patterns are not electricallyconnected to the MISFET, wherein the bump electrode of the semiconductorchip and the electrode of the glass substrate are electrically connectedvia an anisotropic conductive film formed between the semiconductor chipand the glass substrate.
 30. A semiconductor device according to claim29, wherein the first patterns and the second patterns are dot-shaped,respectively.
 31. A semiconductor device according to claim 29, whereinthe first patterns and the second patterns are positions directly underthe alignment mark.
 32. A semiconductor device according to claims 29,wherein the semiconductor device is an LCD driver for a liquid crystaldisplay device.
 33. A semiconductor device according to claims 29,wherein the semiconductor substrate has four corners, wherein thealignment mark is formed in a vicinity of one of the four corners,wherein a guard ring is formed in the same layers as the first wiringlayer, the second wiring layer and the third wiring layer, wherein theguard ring is formed so as to surround the alignment mark formationregion and the integrated circuit formation region, wherein thealignment mark formation region is arranged between the guard ring andthe integrated circuit formation region, and wherein the integratedcircuit formation region is not arranged between the alignment markformation region and the guard ring.
 34. A semiconductor deviceaccording to claims 29, wherein the third wiring layer and the alignmentmark are formed in a top wiring layer.
 35. A semiconductor deviceaccording to claims 29, wherein a thickness of the first patterns aresmaller than a thickness of the alignment mark, and wherein a thicknessof the second patterns are smaller than the thickness of the alignmentmark.